In the Montessori Casa, or classroom for three through six year old students, children ages four and older use color-coded beads, slotted boards, and wooden number cards to concretely learn quantities and numeric symbols for teen numbers eleven through nineteen following ample experience with quantities and numbers one through ten. My First Montessori Book of Teen Numbers, the sequel to My First Montessori Book of Quantities and My First Montessori Book of Numbers, is designed to help children strengthen their understanding of the first few numbers beyond ten in preparation for more advanced mathematics exercises. Written and illustrated by AMI Primary Diploma holder Mary Da Prato, My First Montessori Book of Teen Numbers describes strategies used in the Casa to help children learn and understand teen numbers as an essential prerequisite for counting to 1,000 and beyond.